1. Field of the Invention
This invention relates to an optical information recording device, optical information playback device, and optical information recording medium such as for use with compact disks and their recording units and playback units. This invention regulates the timing and intensity of the laser beam, records the main data by means of the pit and mark length and intervals and effectively prevents illegal copying by recording identification data by means of the width of the pits and marks.
2. Description of Related Art
Conventionally, as for instance in the compact disk which is one type of optical information recording medium, after data processing of the data accompanying the recording, EFM (Eight-to-Fourteen) modulation is performed against the fundamental period T, a row of bits for a period 3T to 11T are formed, and by this process the audio data recorded.
In contrast, in compact disk players, a laser beam is irradiated upon a compact disk and the returning light received, a playback signal is obtained whose signal level is altered according to the intensity of this returning light, and a binarizing signal generated by binarizing of this playback signal to a specified slice level. Further, a PLL (phase lock loop) circuit is driven by this binarizing signal and a playback clock pulse generated. The binarizing signal is sequentially latched by this playback clock pulse and this process generates playback data at a period of 3T to 11T corresponding to the pit row formed on the compact disk.
The playback data, generated in this way in the compact disk player is decoded by data processing corresponding to the data processing during recording, and playback such as of audio data recorded in the compact disk can be performed.
Such kind of compact disks have information such as the manufacturer's name, manufacturing location, and disk number stamped on a zone on the inner side of the lead-in area on which data cannot be recorded. This stamped information allows visual identification as to whether the compact disk is being used for illegal copying.
However illegal copying generally consists of two types. In one type, a stamper is manufactured from audio data obtained by playback of a genuine compact disk and the copy of the compact disk then made. In the other type, a physical copy is made of the pit shape formed on the genuine optical disk.
In these two types of illegal copying, identifying an illegal copy is difficult when even the stamp itself has been copied. Further, even without this stamp the audio data can be played back so preventing this type of illegal copying is extremely difficult.